Repetitive transcranial magnetic stimulation (rTMS) has been used with the goal of treating depression, see, e.g., George et al., The Journal of Neuropsychiatry and Clinical Neurosciences, 8:373, 1996; Kolbinger et al., Human Psychopharmacology, 10:305, 1995.
One example of an rTMS technique uses a figure-8 surface coil with loops that are 4 cm in diameter (Cadwell, Kennewick, Wash.). This coil is placed next to the scalp, and is usually positioned to direct the magnetic field at the prefrontal cortex of the brain, see, e.g., George et al., The Journal of Neuropsychiatry and Clinical Neurosciences, 8:373, 1996. An electric current is run through the magnetic coil to generate a magnetic field, specifically a sequence of single-cycle sinusoidal pulses where each pulse has a frequency of approximately 1800 Hz (or about 560 microseconds per pulse). These pulses are delivered at a repetition rate of 1 to 20 Hz (i.e., one pulse every 0.05 to 1 second), see, e.g., George et al, Biological Psychiatry, 48:962, 2000; Eschweiler et al, Psychiatry Research: Neuroimaging Section, 99:161, 2000.
Some subjects have declined participation in rTMS studies due to pain induced in the scalp. In addition, seizures have been reported as a result of rTMS treatment, see, George et al, Biological Psychiatry, 48:962, 2000; Wasserman, Electroencephalography and Clinical Neurophysiology 108:1, 1998.